1996, which was studied by the University of Leicester, England. They found that the speed of the hourglass is only related to the sand a few centimeters above the neck, but not to the total amount of sand. Then they replaced all the grains of sand with small glass balls. If all the small glass balls are equal in size, the overall timing length of the hourglass is related to the following three factors: the overall volume of the glass ball, the opening size and the shape of the hourglass.
If the opening diameter of the hourglass is more than 5 times the diameter of the small glass ball, they also satisfy the relationship P = kV (d-d)-2.5, where P is the length of time, K is the proportional coefficient related to the shape of the hourglass, V is the volume of the whole glass, D is the opening diameter of the neck, and D is the diameter of the glass ball. If it is an hourglass in the shape of a wine bottle, the proportional coefficient k is about 2 1.
Extended data
The factors that affect the time hourglass include: the amount of filler, the bending shape of the inner wall of the glass ball (the timing length of the hourglass is slightly different when it is upright and inverted), the width of the neck tube, the type and quality of filler. The earliest hourglass used ancient tomb marble grinding powder, iron filings and eggshell powder. Modern hourglasses usually use artificial glass beads. ?
According to the specification document of German hourglass manufacturer KOCH, the error of 30-minute hourglass can be controlled within 1 minute, and the error of 1 hour hourglass is about 5 minutes. Note: it is not a timing instrument, and can be compared with the accuracy of modern timing instruments.
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